The cooling channels that are adjacent to a combustion chamber wall normally have the objective of keeping the combustion chamber wall so cool relative to the hot combustion gases that a sufficiently long service life of the combustion chamber is ensured. Various solutions are known from the state of the art for achieving this objective.
German patent application DE 100 54 333 A1 discloses a combustion chamber with a cooling unit as well as with an inner combustion chamber wall adjacent to the interior of the combustion chamber for a regeneratively cooled engine. The inner combustion chamber wall has depressions that are configured in such a way that a stable gas stream formed in the area of the inner combustion chamber wall during operation of the combustion chamber becomes destabilized in terms of its flow in the area of the depressions. This approach is based on the consideration that the gas stream in the combustion chamber forms a boundary layer in the area of the combustion chamber wall in the normal case of a smooth combustion chamber wall, said boundary layer having a certain thermal insulating effect against the heat input into the combustion chamber wall resulting from the hot gas stream. With that arrangement, an endeavor is made to disrupt the formation of this thermally insulating boundary layer so as to increase the heat input into the combustion chamber wall and thus into the cooling unit. However, from the standpoint of manufacturing, creating depressions inside the combustion chamber is technically difficult and expensive.
Furthermore, German patent application DE 101 56 124 A1 discloses a rocket engine with a combustion chamber and an expanding nozzle, said combustion chamber and/or said expanding nozzle having cooling channels for cooling with a liquid. In order to reduce temperature layering (stratification) in the cooling medium, it is provided that at least some of the cooling channels have a meander-like geometry, at least in sections. As a result of a curvature of the cooling channel, centrifugal forces and Coriolis forces are induced by the resultant flow deflection as a function of the local curvature radius, said forces manifesting themselves in the formation of a vortex pair situated in the flow cross section. This vortex pair ensures a convective flow exchange within the cross section, as a result of which stratification is reduced. However, the production of meander-like cooling channels calls for additional effort and raises the costs.
Finally, world patent application WO 02/055864 A1 describes providing the cooling channels with a surface that guides the cooling medium. The guide surface imparts the coolant with a rotation when it flows through the cooling channel so that a stratification is prevented. In order to create the guide surface, it is provided that a metal film is shaped into the desired form with the guide surface and this intermediate product is configured as cooling channels and applied onto a combustion chamber wall. Here, the guide surface is formed by protruding ribs that are at an angle relative to the axis of the cooling channel. Instead of ribs, it is also proposed that the surface be provided with notches or grooves. These, too, extend at an angle relative to the axis of the cooling channel in order to impart the desired rotation to the cooling medium.
Hence, in order to attain an improved heat transfer from the combustion chamber into the cooling medium of a cooling unit, design measures are implemented in an attempt to prevent temperature layering in the area of the combustion chamber wall—either in the combustion chamber itself or in the cooling unit. However, the measures proposed in the state of the art have drawbacks in terms of their handling and production.